The present invention relates generally to methods and apparatus for forming parts of a predetermined shape, such as drill bits and, more particularly, spade-type boring bits, from a continuous stock material. The present invention also relates generally to improved forges for forming parts of a predetermined shape, such as drill bits and, more particularly, spade-type boring bits.
Each day, a myriad of metal and plastic parts of a variety of predetermined shapes are manufactured, such as by a forging process in which a permanent change in the shape of the part occurs. These parts are oftentimes manufactured in large quantities and are used in many different applications. For example, a number of tools, such as drill bits, screwdriver bits, router bits, percussion bits and jigsaw and reciprocating saw blades, are produced in mass quantities every day. Likewise, a number of other parts, such as fasteners, impact wrench anvils, coil and ballpoint chisels, gears, shafts, equalizer beams and actuator rods, are also manufactured in large quantities every day.
Accordingly, a number of manufacturing processes have been developed to form parts of a predetermined shape in large numbers. These manufacturing processes generally include a number of independent operations or steps which are performed in a predetermined sequence in order to create parts of the desired shape. For example, typical processes for manufacturing metal parts generally include forging operations, trimming operations, heat-treating operations and grinding and other finishing operations.
These manufacturing processes are typically designed to form a number of discrete workpieces into respective parts of a predetermined shape. Thus, these conventional manufacturing processes generally include an initial step of providing a number of discrete workpieces of the desired size and length. For example, a metal wire or rod can be cut into a number of discrete pieces prior to beginning the actual manufacturing process. Thereafter, the plurality of discrete workpieces are individually processed in order to create a plurality of parts of the predetermined shape.
As a result, each discrete part must generally be collected following every operation of these conventional manufacturing processes such that the part can be transported to the next stage or operation of the manufacturing process. In addition, since the parts must generally be aligned in a predetermined manner during each operation of these manufacturing processes, each part must generally be individually oriented prior to each next stage of the manufacturing process. Thus, even though parts are generally collected and transported between stages of these manufacturing processes in batches, these conventional manufacturing processes still generally require extensive handling of the parts in order to collect, transport and properly orient the parts between each stage of these manufacturing processes. These conventional manufacturing processes also typically require a relatively large number of parts to be in process at all times due to the batch-type processing. As will be apparent, the time and labor required to collect, transport and properly orient parts during these conventional manufacturing processes decreases the efficiency with which these parts are fabricated and, correspondingly, increases the cost of the resulting parts.
The inefficiencies created by handling and processing a plurality of discrete parts and the increased costs of maintaining a relatively large number of partially formed parts in process are particularly significant for those manufacturing processes which are designed to produce a large number of parts each day, such as tens of thousands, if not hundreds of thousands, of parts each day. For example, conventional manufacturing processes which produce metallic parts, such as drill bits, router bits, fasteners, percussion bits, jig saw and reciprocating saw blades, impact wrench anvils, coil and ballpoint chisels, gears, shafts, screwdriver bits, equalizer beams and actuator rods, generally produce parts at rates up to thousands or more per day.
In order to demonstrate the inherent inefficiencies of these conventional manufacturing processes which individually process a large number of discrete parts, the manufacturing process employed to form spade-type boring bits (hereinafter referred to as xe2x80x9cspade-bitsxe2x80x9d) is described hereinafter. Spade bits are typically formed by a hot forging process. According to this process, a coil of wire stock of a given diameter is cut into pieces, each of which is approximately the length of an individual spade bit. Each piece is then headed to form a portion of material with an increased diameter at the first end of the segment, i.e., a bulb of material having an increased diameter over a shorter length at the first end. Either during this initial heated process or following further heating of the bulb of material, the part is forged by compressing the heated bulb of material between a pair of opposed dies. Typically, the pair of opposed dies are closed in a rectilinear manner such that the heated bulb of material is subjected to compressive forces which displace the material into the predetermined fixed boundary shape defined by the dies. The forged part can then be trimmed and finished to produce spade bits such as those described above. An identification mark can also be stamped on the spade bit during its processing.
By initially cutting the wire stock and/or billets into a number of discrete pieces, however, the parts must be individually handled and processed throughout the hot forging process, thereby decreasing the efficiency with which the spade its are fabricated and, correspondingly, increasing the resulting costs of the spade bits. For example, each individual part must be collected following each stage of the fabrication process and transported to the next stage. In addition, each individual part must be appropriately aligned during each step of the process to ensure that the input shape of the part serves as a proper and admissible preform to satisfy the requirement of each subsequent die operation, including die fill, such that the resulting spade bits meet the desired product tolerances.
A method and apparatus is therefore provided according to the present invention for forming a plurality of parts, such as spade bits, from a continuous stock material. Thus, the various steps of the forming method of the present invention can be performed to predetermined portions of the continuous stock material, prior to separating the continuous stock material into a number of discrete parts. The efficiency of the forming process is thereby enhanced since individual parts need not be transported and oriented numerous times during the forming operations. By not requiring that the individual parts be handled during the forming operations, the quality and tolerance control of the parts formed by the forming method and apparatus of the present invention will also be enhanced since such handling of individual parts generally increases the opportunities for misalignment and contributes to poor tolerance control during the manufacturing process. In addition, the forming method and apparatus of the present invention effectively reduces the number of parts in process at any one time during the manufacturing process by limiting the number of batch operations required in comparison to conventional fabrication processes.
According to the forming method and apparatus of the present invention, a plurality of indexers are synchronized to incrementally advance the continuous stock material along a predetermined path such that the stock material advances longitudinally in a downstream direction. Following each intermittent advance of the continuous stock material, a portion of the continuous stock material is formed, such as with a forge, into a first predetermined shape.
According to this embodiment of the present invention, the plurality of indexers include an upstream indexer for intermittently pushing the continuous stock material in the downstream direction from a location spaced in an upstream direction from the forge. Additionally, the plurality of indexers include a downstream indexer for intermittently pulling the continuous stock material in a downstream direction from a location spaced in the downstream direction from the forge. By synchronizing the intermittent pushing and pulling, the continuous stock material is advanced longitudinally in the downstream direction along the predetermined path. By synchronously pushing and pulling the continuous stock materials from locations that are upstream and downstream of the forge, respectively, the forming method and apparatus of the present invention advances the continuous stock material more smoothly in the downstream direction and significantly reduces the possibility that the continuous stock material will kink or bend relative to conventional forming processes which utilize a single upstream indexer.
Preferably, the upstream indexer intermittently pushes continuous stock material by a predetermined distance in the downstream direction and the downstream indexer intermittently pulls the continuous stock material by the same predetermined distance in the downstream direction. As such, the continuous stock material can be intermittently advanced by the predetermined distance each time that the continuous stock material is pushed and pulled by the respective indexers. Additionally, the upstream and downstream indexers are preferably synchronized such that the upstream and downstream indexers concurrently pull and push the continuous stock material in a downstream direction, respectively.
The forming method and apparatus generally includes a clamp for securely gripping and holding a fixed portion of the continuous stock material while another portion of the continuous stock material is formed into the first predetermined shape. According to the present invention, the clamp and, more particularly, the fixed portion of the continuous stock material held by the clamp is disposed in a predetermined longitudinal direction relative to the formed portion of the continuous stock material which is shaped into the first predetermined shape.
As a result of processing a continuous stock material, the continuous stock material grows in both longitudinal directions during the forming operations. According to the present invention, however, the longitudinal growth of the continuous stock material created during the forming operation is at least partially compensated for by allowing movement of the continuous stock material in a longitudinal direction opposite the predetermined longitudinal direction established by the relative positions of the fixed portion of the continuous stock material and the formed portion of the continuous stock material. By compensating for the longitudinal growth of the continuous stock material, the forming method and apparatus of the present invention can form the continuous stock material into a plurality of parts prior to separating the stock material into the plurality of discrete parts, thereby increasing the manufacturing efficiency of the parts.
The forming apparatus of the present invention also preferably includes a longitudinal growth monitor for monitoring the longitudinal growth of the continuous stock material during forming operations. The forming apparatus also advantageously includes a controller, responsive to the longitudinal growth monitor, for terminating forming operations once the longitudinal growth of the continuous stock material is at least as great as a predetermined growth threshold.
Accordingly, the forming method and apparatus of the present invention can readily manufacture parts of a predetermined shape and size in a precisely controlled fashion.
According to one embodiment, the forge includes a die assembly including a plurality of dies disposed about the continuous stock material and means for at least partially closing the plurality of dies about the stock material. Once closed, the plurality of dies define a cavity of a predetermined shape which, in turn, defines the shape of at least a portion of the resulting part. According to the present invention, the plurality of at least partially closed dies also define entry and exit ports through which the continuous stock material extends.
The means for at least partially closing the plurality of dies about the continuous stock material preferably includes a ram having a die housing which defines a die cavity opening through the forward end of the ram and adapted to receive and circumferentially encompass the plurality of dies, thereby structurally reinforcing the forging dies during the forging process. Thus, by at least partially inserting the plurality of dies within the die cavity defined by the ram, the plurality of dies can be at least partially closed about the continuous stock material.
The forge also generally includes a head which defines a passageway extending lengthwise through at least a portion of the head and defining a lengthwise extending axis. As such, the ram can be alternately advanced and retracted within the passageway defined by the head during forging operations. During the lengthwise advancement of the ram, the die assembly will be further inserted into the die cavity and the forging dies will be correspondingly forced radially inward in order to forge the part of the predetermined shape. Similarly, during the retraction of the ram following completion of the forging operations, the die assembly will be at least partially removed or withdrawn from the die cavity such that the forging dies can move radially outwardly away from the continuous stock material.
The forge of the present invention also preferably includes a carriage on which the head, the ram and the plurality of dies are mounted. The carriage is mounted to move in a longitudinal direction relative to the continuous stock material. As a result, the carriage can move in a longitudinal direction opposite the predetermined longitudinal direction established by the relative positions of the fixed portion of the continuous stock material and the formed portion of the continuous stock material in order to further compensate for the longitudinal growth of the continuous stock material created during the forming operations. In particular, the carriage is adapted to move to compensate for the longitudinal growth of that portion of the continuous stock material between the formed portion of the continuous stock material and the fixed portion of the continuous stock material. As a result of this longitudinal movement of the carriage, the plurality of dies remain at least partially closed about the same portion of the stock material during the entire forming step.
According to one advantageous embodiment, the forge also includes biasing means for longitudinally biasing the carriage with a predetermined longitudinal bias force so as to retard the longitudinal movement of the carriage. According to one aspect of the present invention, the longitudinal bias force applied by the biasing means can be altered according to a predetermined schedule. For example, the biasing means can increase the longitudinal bias force over time to encourage lateral expansion of the workpiece within the cavity defined by the plurality of dies such that the entire cavity is filled.
While the clamp continues to hold the fixed portion of the continuous stock material, the forming method and apparatus of the present invention can form another portion of the continuous stock material into a second predetermined shape, such as with a second forge. Once both portions of the continuous stock material have been formed, the clamp can release the fixed portion of the continuous stock material such that the continuous stock material can be further advanced along the predetermined path. Thereafter, the steps of the forming method can be repeated such that parts which have both the first and second predetermined shapes can be fabricated in mass.
According to one advantageous embodiment of the present invention, the continuous stock material includes a number of longitudinally spaced apart registration features. For example, the continuous stock material can include a registration feature defined between those portions of the continuous stock material which will be formed into respective ones of the plurality of parts by the forming method and apparatus of the present invention.
Accordingly, the forming apparatus of one advantageous embodiment of the present invention can include a sensor for identifying a registration feature on the continuous stock material. According to this embodiment, the forge can therefore include a positioner for positioning the forge such that the portion of continuous stock material which is formed is longitudinally spaced from the registration feature identified by the sensor by a predetermined distance. Likewise, the clamp of the forming apparatus of this embodiment of the present invention can also include a positioner for positioning the clamp such that the clamp securely grips a fixed portion of the continuous stock material which is longitudinally spaced from the registration feature by a predetermined distance.
The forming method and apparatus of one embodiment of the present invention can also include trimming means, such as a trimmer, disposed downstream of the forge for trimming predetermined portions of each part. The trimmer can also include a positioner for positioning the trimmer such that the predetermined portions which are trimmed are spaced from the registration feature by a predetermined distance. Likewise, the forming apparatus of one embodiment can include a cutter, disposed downstream of the first and second forges, for cutting the continuous stock material following formation of the parts so as to thereby separate the continuous stock material into a plurality of discrete parts. As described above in conjunction with the forge, clamp and trimmer, the cutter can include a positioner for positioning the cutter such that the portion of the continuous stock material which is cut is longitudinally spaced from the registration feature by a predetermined distance. By identifying the registration features defined by the continuous stock material, the various operations of the forming method and apparatus of the present invention can be performed in a precise manner on predetermined portions of the continuous stock material.
According to one advantageous embodiment of the present invention, an apparatus is provided for trimming and separating the plurality of parts formed from a continuous stock material which includes a plurality of longitudinally spaced apart registration features. The apparatus of this embodiment includes a trimmer for trimming predetermined portions of each part and a separator such as a snipper, a saw or other cutter, disposed downstream of the trimmer for separating each part from the continuous stock material once predetermined portions of the part have been trimmed. Advantageously, the separator is operably connected to the trimmer such that the separator and the trimmer are moved together in the longitudinal direction. However, the apparatus of this embodiment preferably includes a positioner for positioning the separator relative to the trimmer such that the trimmer and separator can be appropriately spaced, such as to process parts of different lengths. In order to properly position the trimmer and the separator, the apparatus of this embodiment also includes a sensor for identifying a registration feature on the continuous stock material and a positioner, responsive to the sensor, for jointly positioning the trimmer and the separator such that the portion which is trimmed and the position at which a part is separated from the remainder of the continuous stock material are longitudinally spaced from the registration feature by a predetermined distance. By moving the trimmer and the separator as a unit, the apparatus of this embodiment of the present invention simplifies the overall design of the forming method and apparatus by reducing the number of components which must be individually positioned relative to the registration features of the continuous stock material.
In addition to positioning the trimmer and the separator relative to the registration features of the continuous stock material, the positioner also permits the trimming and separating station to serve as an indexer. In this regard, the trimmer securely holds the continuous stock material while predetermined portions are trimmed. While the trimmer is securely holding the continuous stock material, the positioner can therefore advance the trimmer and the separator in the downstream direction in order to effectively pull the continuous stock material along the predetermined path. Correspondingly, the forming apparatus can include an indexer which also intermittently advances the continuous stock material in the downstream direction, such as by pushing the continuous stock material along the predetermined path, as described above. By synchronizing the indexer and the positioner of the trimming and separating station, the continuous stock material can be concurrently advanced in the downstream longitudinal direction by both the indexer and the positioner.
According to one advantageous embodiment of the present invention, at least one forging die includes a contact surface which defines a portion of the cavity for contacting and shaping the workpiece into the predetermined shape of the resulting part. More often, the plurality of forging dies include at least two forging dies, such as upper and lower forging dies, which include respective contact surfaces to deform and shape the workpiece upon actuation or closing of the forging dies. According to this embodiment of the present invention, the plurality of forging dies are moved inwardly in a predetermined direction as the forging dies are inserted within the die cavity defined by the ram, thereby at least partially closing the forging dies about the continuous stock material. The predetermined inward direction in which the forging dies move is preferably oblique to the respective contact planes of the forging dies. For example, the contact plane of at least one forging die and a reference plane perpendicular to the predetermined direction of movement of the forging die define an angle of between about 10xc2x0 and about 20xc2x0 therebetween, according to one advantageous embodiment. The respective contact surfaces therefore impart both axial and radial forces to at least portions of the workpiece to form the part of predetermined shape within the cavity defined between the plurality of forging dies. Due to the shape of the contact surfaces and the resulting orientation of the axial and radial forces applied, compressive, tensile and shear forces are generated within the workpiece which facilitate the efficient formation of the part of predetermined shape. Accordingly, thin parts which have a relatively large diameter can be readily forged according to this aspect of the present invention. Further, the power required to forge parts of a predetermined size and shape is reduced in comparison to conventional compressive forging processes by imparting compressive, tensile and shear forces at desirable locations within the workpiece.
In addition to the inner contact surface, each forging die preferably includes an opposed back surface having a predetermined shape for operably contacting those portions of the ram which define the die cavity. According to one embodiment of the present invention, the back surface of the forging dies have been advantageously designed to include a medial section having a partial conical shape. In addition, the back surface includes first and second lateral sections disposed on opposite sides of the medial section. Each lateral section preferably also has a partial conical shape. However, the radius defined by the conical medial section is larger than the radius defined by the conical lateral sections at each corresponding location along the length of the forging die. As such, the back surface of the forging die of this advantageous embodiment no longer presents a continuously smooth surface across the entire back surface. In addition, the first and second lateral sections are recessed relative to the medial section.
Since the forging die is typically tapered such that the contact surface is separated from the back surface by a greater amount at a first end of the forging die than at a second end of the forging die, the medial section of the back surface of this advantageous embodiment is also preferably tapered so as to be wider proximate the first end of the forging die and narrower proximate the second end of the forging die. As a result, the medial section has a trapezoidally shaped surface. As a result of the unique construction of the back surface of the forging die, the forging die advantageously contacts those portions of the ram which define the die cavity in a relatively even manner across most, if not all, of the conical medial section of the forging die as opposed to conventional forging dies which contacted the ram in a much smaller area, thereby significantly increasing the forces applied to at least portions of the forging die and correspondingly increasing the wear of the die and decreasing the effective lifetime of the die.
According to one aspect of the present invention, an improved forge is provided. According to one embodiment, the interior surface of the head and the exterior surface of the ram cooperate to define a clearance region proximate the forward end of the ram which permits a slight deflection of the forward portion of the ram in a radially outward direction as the ram is advanced over the die assembly. In particular, the clearance region defines a larger gap between the head and the forward portion of the ram than exists between the head and other portions of the ram, thereby reducing, if not eliminating, interference between the forward portion of the ram and the head. However, a portion of the ram is preferably maintained in an interference fit with the head so as to guide the ram during its lengthwise advancement and retraction. For example, the head can include a bronze bushing for engaging the ram and for providing the interference fit therewith.
In one embodiment, the head defines a circumferentially extended groove opening into the passageway at a location proximate the forward end of the ram. In this embodiment, the groove defines the clearance region to permit slight radially outward deflection of the forward end of the ram during forging operations. Preferably, the circumferential groove extends from a first location at least as forward as the forward end of the ram following the lengthwise advancement of the ram to a second location at least as rearward as a location corresponding to the position to which the plurality of forging dies are inserted into the die cavity defined by the ram following the lengthwise advancement of the ram.
The forge of another embodiment includes a rotator for imparting an incremental relative rotation between the ram and the die assembly after at least one part has been forged. Typically, the rotator incrementally rotates the ram about the lengthwise extending axis after at least one part has been forged. In this regard, the ram is preferably rotated while the ram is retracted and the forging dies have moved outwardly so as to no longer engage the workpiece. By repeatedly rotating the ram in increments, the rotator eventually rotates the ram through a full 360xc2x0.
The ram is preferably incrementally rotated after a predetermined number of parts have been forged. For example, the ram can be incrementally rotated after forging each part. While the ram can be rotated in different degrees, the ram of one embodiment is rotated between 10xc2x0 and 30xc2x0 and, more preferably, is rotated about 20xc2x0 about the lengthwise extending axis during each incremental relative rotation. The ram can be rotated in a variety of manners. In one embodiment, for example, a gear can be operably connected to the ram and a drive member, such as a ratchet or a pinion gear, can be driven so as to engage the gear and to cause the gear to rotate, thereby correspondingly rotating the ram relative to the die assembly.
For control purposes, the forge can also include a sensor for detecting the incremental relative rotation between the ram and the die assembly. As such, the forge can delay the lengthwise advancement of the ram through the passageway defined by the head until after the sensor has detected that the ram has been rotated relative to the die assembly.
By rotating the ram through the entire 360xc2x0, the shape of the ram, typically a cylindrical shape, is maintained and the ram is prevented from developing an oval shape as a result of the forces imparted during forging operations. Thus, the forge of this embodiment of the present invention can more reliably form parts of the predetermined shape over a longer period of time, thereby extending the effective life of the ram.
According to one advantageous embodiment of the present invention, the forge includes a lubrication system for providing a lubricant between at least some of the forging dies and the ram. By lubricating the forging dies and the ram, the lubrication system facilitates the relative movement between the ram and the forging dies which occurs as the ram is alternately advanced and retracted. Preferably, the lubrication system provides lubricant while the ram is at least partially retracted and the die assembly is at least partially removed from the die cavity since the die assembly and, more particularly, the forging dies will then be exposed beyond the ram.
In one embodiment, the ram defines a plurality of ports opening into the cavity. As such, the lubrication system can inject lubricant through the ports so as to provide lubricant between at least some of the forging dies and the ram. In the embodiments in which the forge also includes a rotator for imparting an incremental relative rotation between the ram and the die assembly, the relative rotation between the ram and the die assembly will also therefore serve to circumferentially distribute the lubricant which has been injected at a number of discrete points in a fairly even manner.
The lubrication system can also provide lubricant between the ram and the head to facilitate relative movement therebetween, i.e., to facilitate the alternate advancement and retraction of the ram relative to the head. In this embodiment, either the head, the ram or both the head and the ram can define at least one circumferentially extending groove opening into the passageway defined by the head. As such, the lubrication system can inject lubricant into the circumferential groove for distribution between the head and ram as the ram is alternately advanced and retracted during forging operations.
As such, the forging apparatus of this embodiment facilitates relative movement between the ram, the die assembly and the head so as to reduce the wear of the various components and to correspondingly extend the operational life of the forge. In contrast to conventional wisdom which discouraged the use of lubrication during a continuous forming process for fear of coating the stock material with a lubricant which might prevent or impair proper handling and positioning of the stock material, the forging apparatus of this embodiment of the present invention lubricates the various components of the forge while permitting only a minimal amount of the lubricant to contact the continuous stock material such that subsequent handling and positioning of the continuous stock material is not adversely affected.
As will be apparent, the forming method and apparatus of the present invention is extremely versatile and can form a variety of different types of parts from a continuous stock material. According to one advantageous embodiment, however, the forming method and apparatus forms spade bits of a predetermined shape. In particular, the spade bit can include an elongate shank defining a central longitudinal axis and a blade portion joined at a rear end to one end of the shank. The spade bit can also include a spur extending axially from a forward end of the blade portion, opposite the rear end.
The blade portion of the spade bit of the present invention includes a pair of generally flat side segments which extend laterally in opposite directions from the central longitudinal axis. The side segments define respective lateral planes which are parallel to each other and the central longitudinal axis. The side segments also include respective forward cutting edges which are axially offset relative to each other to thereby define an axially advanced forward cutting edge and an axially rearward forward cutting edge. According to one advantageous embodiment, the forward cutting edges are axially offset by a predetermined axial offset, such as between about 0.010 inch and about 0.012 inch. By having forward cutting edges which are axially offset, the spade bit can more efficiently engage and remove portions of a workpiece during the boring of a hole. As a result, the longevity of a spade bit having axially offset forward cutting edges is also generally enhanced due to the more efficient removal of chip swarf during drilling operations.
The side segments of the blade portion of the spade bit of the present invention can also include chamfered corner portions which include a chamfered edge extending both axially rearward and laterally outward from the respective forward cutting edge. In addition, each chamfered corner portion can include a chamfered surface which slopes radially inward from the respective chamfered edge to a rear edge. By including chamfered corner portions, the spade bit of the present invention can more cleanly bore a hole while reducing binding and other frictional engagement between outer portions of the spade bit and the inner periphery of the hole, thereby further increasing the efficiency of the drilling operations.
Regardless of the type of parts formed by the forming method and apparatus of the present invention, the forming method and apparatus can effectively form a plurality of parts of a predetermined shape from a continuous stock material without separating the parts until most, if not all, of the forming operations have been completed. As a result, the forming method and apparatus of the present invention significantly increases the efficiency with which parts of a predetermined shape are manufactured, as well as the tolerance control and concomitant quality of the resulting parts. In addition, the forming method and apparatus of the present invention effectively decreases the number of partially formed parts which are in process at any one time, thereby further increasing the efficiency and decreasing the costs associated with the manufacture of parts of the predetermined shape according to the forming method and apparatus of the present invention.